After students were sent home, the school got a call from Vanderbilt University Children's Hospital, saying several students had been brought in and showed high levels of carbon monoxide.

Hospital spokesman Craig Boerner said 49 students were eventually brought in by parents and 40 of them were admitted. There were no fatalities and all of the students were in stable medical condition.

"Dr. Donna Seger, who is the hospital toxicologist and also the medical director of the poison control center, said the treatment would be 23 hours of oxygen," Boerner said.

"The hospital advised parents to take their children to any hospital for treatment," he said.

Boerner said it was important for parents of Drexel students to have their children examined by doctors if they weren't feeling well because the symptoms of carbon monoxide poisoning can mimic those of influenza.

Workers found a hole in a heating unit that serves the central part of the school and it was being repaired.

Carbon monoxide is a colorless, odorless gas produced by combustion.

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